good reply -- thanks for the help -- I'm sure he appreciated your input. ______________________________ Reply Separator _________________________________ Subject: Soldering Alloy 42 lead frames Author: [log in to unmask] at SMTPpost Date: 9/23/96 12:11 PM To: Randy Johnson Woodward Governor Co. Loveland Co. Here at Smiths Industries, Grand Rapids, Mi. we are using Intel TSOPs with Alloy 42 lead frames in a military avionics environment. Our typical thermal cycle is 5 hours from -55 to 95 deg C with 2 hour dwells at the extremes. Early in the program we found solder joint failures at as few as 28 thermal cycles. Failure analysis directly attributed the failures to the poor solderability of Alloy 42 and lack of coefficient of thermal expansion(CTE) matching between the device and PWB. We had Intel come in with their local rep and 2 factory people. We explained our problem and asked of they would consider using copper lead frames. The response was that their largest TSOP customer was AT&T and that AT&T had been asking for the same change for the same problem. They went on to say there were no plans at Intel to ever change this device's lead frame material. (I have noticed that the new suffix 'DD' part has a copper lead frame.) One of the factory people said we could improve solderability by using a more active flux and higher soldering temperatures. Being a military product we have been restricted to RMA. We solved our CTE problem by adding copper-invar-copper foil layers to the PWB. We have since successfully completed 500 thermal cycles, which we consider a life test. We continue to have difficulty soldering to the Alloy 42 and have had to give extra training to the solder operators and inspectors. I have spoken with a reliability engineer at Rockwell Collins and was told they had problems with these parts and have prohibited the use of TSOPs. S. Holen Packaging Engineer Smiths Industries email: [log in to unmask] *************************************************************************** * TechNet mail list is provided as a service by IPC using SmartList v3.05 * *************************************************************************** * To unsubscribe from this list at any time, send a message to: * * [log in to unmask] with <subject: unsubscribe> and no text. * *************************************************************************** *************************************************************************** * TechNet mail list is provided as a service by IPC using SmartList v3.05 * *************************************************************************** * To unsubscribe from this list at any time, send a message to: * * [log in to unmask] with <subject: unsubscribe> and no text. * ***************************************************************************